To investigate the mechanism of the interaction between skeletal muscle and bone. The study should provide insight into this mechanism and also the influence of testosterone replacement on skeletal muscle and bone mass in postmenopausal women. The desing is a double-blind, placebo-controlled trial. 40 postmenopausal female subjects will be randomly assigned to exercise-only, exercise + testosterone, testosteone-only, or control. The intervention will be 4 months, with exercise involving 40 minutes of resistance training 3x per week and testosterone involving replacement dosages of 0.88 grand daily transdermal application.